1. Field of the Invention
This invention relates to a reactor for dewatering and aerobically biodegrading organic and oily sludges.
2. Description of the Prior Art
Composting is a thermophilic biological process used for the treatment of municipal sludges. Many composting systems are available, but the process almost always involves mixing the sludge with a bulking agent and then using forced aeration to eliminate noxious odors caused by anaerobic decay and to maintain sufficient oxygen so that the elevated temperatures necessary to the composting process can be obtained. Oily sludges can be composted; however, it has been shown that no decomposition rate advantage is obtained over ambient aerobic processes that dispose of oily sludges.
Landfarming is an economical and widely used method for the disposal of organic and oily sludges. This method involves applying sludge to soil and tilling the soil to allow aerobic bacteria to convert the organic fraction into carbon dioxide, water, and humic matter. Frequent tilling of the soil allows air to diffuse to the bacteria preventing anaerobic conditions and the subsequent formation of odorous products.
Although environmentally sound, landfarming has certain disadvantages. Landfarms are open systems. Their operation has an effect on the soil, air and groundwater at the treatment site. Governmental regulations have been put in place to minimize any negative impact of landfarming on the environment. These regulatory limitations on the oil loading rate based on heavy metals or nitrogen concentration can dictate the size or lifetime of a landfarm. Odor generation or the proximity of groundwater supplies may restrict the location of a landfarm. To demonstrate that a landfarm is not adversely affecting the environment, soil, unsaturated zone, and groundwater monitoring must be performed. This is costly and time consuming.
Climate also has an influence on landfarm operations. Cool temperatures slow biological activity. Frozen or muddy soil makes sludge application difficult or impossible by preventing tilling or limiting access of equipment to the landfarm. Excessive soil moisture also limits oxygen transfer.
There is a continuing and until now unsatisfied need for an apparatus to dewater and degrade sludge, particularly low solids content sludge, in an environmentally non-interactive manner. The apparatus must economically handle large volumes of dilute, oily or organic sludges.